Booth structure for coating cathode-ray tube having dust absorbing wall surfaces

ABSTRACT

A coating device for coating a cathode-ray tube with a layer has a booth for accommodating a cathode-ray tube to be coated. The booth houses a coating robot with a spray nozzle for spraying a coating solution onto the cathode-ray tube in the booth to coat a layer on the cathode-ray tube. The inner wall surfaces of the booth are lined with a water-containing member which is supplied with water from a water supply pipe connected to the booth. An air-conditioning unit is mounted on the booth for controlling the temperature and humidity in the booth. The cathode-ray tube is introduced into the booth from a conveyor through an opening defined in a wall of the booth and fitted with a selectively closable door.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coating device for coating thesurface of the screen panel of a cathode-ray tube with a sprayed layersuch as an anti-static layer, an anti-dazzling layer, or the like, andmore particularly to a booth structure for such a coating device.

2. Description of the Prior Art

Cathode-ray tubes have screen panels coated with an anti-dazzling layerfor preventing the screen panel from glaring with reflections and/or ananti-static layer for preventing the screen panel from beingelectrostatically charged with the scanning electron beam emitted fromthe electron gun of the cathode-ray tube. These anti-dazzling andanti-static layers may be coated according to the spray coating process.

Spray coating devices comprise a booth which houses therein a supportbase for supporting an object, such as a cathode-ray tube, to be coatedand a coating robot having a spray nozzle on its arm which is positionedin confronting relationship to the screen panel of the cathode-ray tubeon the support base. In operation, the coating robot moves the spraynozzle to scan the object while spraying a coating solution from thenozzle onto the screen panel to form ether an anti-dazzling layer or ananti-static layer on the screen panel.

When the coating Solution is sprayed over the screen panel, dustparticles in the booth tend to be stirred up and entrained by thesprayed solution. The entrained dust particles are applied, togetherwith the coating solution, to the screen panel. As a result, the qualityof the coated layer on the screen panel may possibly be lower than itshould be.

The anti-dazzling or anti-static layer coated on the screen panel of acathode-ray tube is required to be less glaring than lustrous or moreglossy than anti-glaring, depending on the kind of the cathode-ray tube.The inventor has found that a coating layer can be selected through thecontrol of coating conditions.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a coating devicewhich is capable of coating the screen panel of a cathode-ray tube witha high-quality layer such as an anti-dazzling layer, an anti-staticlayer, or the like in good coating environments, and also of controllingthe type of the coating layer on the screen panel.

According to the present invention, there is provided a coating devicefor coating a cathode-ray tube with a layer, comprising a booth foraccommodating a cathode-ray tube to be coated, spraying means in thebooth for spraying a coating solution onto the cathode-ray tube in thebooth to coat a layer on the cathode-ray tube, a water-containing membermounted on inner wall surfaces of the booth, and water supply meansconnected to the booth for supplying water to the water-containingmember. The water-containing member comprises sponge walls attachedrespectively to the inner wall surfaces of the booth, and water feedpipes disposed in the sponge walls and connected to the water supplymeans. The booth may have a slanted upper wall, one of the sponge wallsbeing attached complementarily to the slanted upper wall.

According to the present invention, there is provided a coating devicefor coating a cathode-ray tube with a layer, comprising a booth foraccommodating a cathode-ray tube to be coated, spraying means in thebooth for spraying a coating solution onto the cathode-ray tube in thebooth to coat a layer on the cathode-ray tube, air-conditioning meanscoupled to the booth for controlling the temperature and humidity in thebooth, and air discharging means for discharging air out of the booth.The air-conditioning means includes an air outlet opening into the boothfor supplying air directly toward the cathode-ray tube. The airdischarging means comprises a hood disposed in the booth for coveringthe cathode-ray tube, and an air discharge port defined in a wall of thebooth adjacent to the hood.

According to the present invention, there is further provided a coatingdevice for coating a cathode-ray tube with a layer, comprising aconveyor for conveying a cathode-ray tube, a booth for accommodating thecathode-ray tube introduced by the conveyor, the booth having an openingdefined in a wall thereof for introducing the cathode-ray tube from theconveyor through the opening into the booth, and a selectively openabledoor disposed in the opening, and spraying means in the booth forspraying a coating solution onto the cathode-ray tube in the booth tocoat a layer on the cathode-ray tube. The conveyor may be disposed onone side of the booth, or extend through the booth.

The above and other objects, features, and advantages of the presentinvention will become apparent from the following description ofillustrative embodiments thereof to be read in conjunction with theaccompanying drawings, in which like reference numerals represent thesame or similar objects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a coating device according to anembodiment of the present invention;

FIG. 2 is an enlarged fragmentary cross-sectional view of a booth of thecoating device shown in FIG. 1;

FIG. 3 is a cross-sectional view of a booth according to anotherembodiment of the present invention;

FIG. 4 is a plan view showing a layout for the coating device shown inFIG. 1;

FIG. 5 is a plan view showing another layout for the coating deviceshown in FIG. 1;

FIGS. 6A and 6B are side elevational views showing different manners inwhich cathode-ray tubes are conveyed by a conveyor; and

FIG. 7 is an enlarged side elevational view, partly in cross section, ofa cathode-ray tube which has been coated with an anti-dazzling layer bythe coating device according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a coating device according to an embodiment of the presentinvention. The coating device, generally designated by the referencenumeral 1, has a substantially fully closed booth 2. The booth 2 housestherein a support base 5 for supporting a cathode-ray tube 3 with animplosion-resistant band such that a screen panel 4 thereof liesvertically, and a coating robot 8 having on its arm a spray nozzle 7 forejecting a coating solution 6. The spray nozzle 7 is disposed inconfronting relationship to the screen panel 4, and can be moved by thecoating robot 8 to scan the screen panel 4 vertically and horizontally.The inner wall surfaces of the booth 2 are lined with a water-containingmember 9, which is a layer of sponge and which member 9 is coupled to awater supply pipe 10.

The water-containing member 9 serves to prevent dust particles frombeing stirred up in the booth 2. As better shown in FIG. 2, thewater-containing member 9 comprises upper, lower, and side sponge walls11 (only one shown in FIG. 2) attached respectively to the upper, lower,and side walls of the booth 2, and water feed pipes 12 (only one shownin FIG. 2) disposed in and extending through the sponge walls 11. Thewater feed pipes 12 have small holes defined in their walls. The waterfeed pipes 12 are connected to the water supply pipe 10 so that water 13can be supplied from the water feed pipes 12 through the holes thereininto the sponge walls 11. All the upper, lower, and side sponge walls 11may be supplied with water from the water feed pipes 12. However, onlythe lower and side sponge walls 11 may be supplied with water from thewater feed pipes 12 so that no water will drop from the upper spongewall 11 into the booth 2. The booth 2 has a water drain port 14 in itslower wall.

FIG. 3 shows another booth 2 combined with a water-containing member 9.The booth 2 includes a slanted upper wall of inverted V-shaped crosssection. In FIG. 3, the water-containing member 9 has an upper spongewall 11 attached complementarily to the slanted upper wall. The uppersponge wall 11 may be supplied with water from the water feed pipes 12because water supplied to the upper sponge wall 11 flows downwardlythrough the upper sponge wall 11, but does not drop into the booth 2a.

As shown in FIG. 1, an air-conditioning unit 17 is mounted on the upperwall of the booth 2. The air-conditioning unit 17 has an air outlet 16positioned above the screen panel 4 of the cathode-ray tube 3 supportedon the support base 5. The air outlet 16 is fitted with an air filter(not shown) of class 100000. The air-conditioning unit 17 controls thetemperature and humidity in the booth 2 through the air outlet 16. Whilethe coating solution 6 is being sprayed onto the screen panel 4 of thecathode-ray tube 3, the air-conditioning unit 17 supplies temperature-and humidity-controlled clean air 19 through the air outlet 16 to thesurface of the screen panel 4. The supplied air is then dischargedthrough a hood 18 and an air discharge port 27 defined in one of theside walls of the booth 2 adjacent to the hood 18. The hood 18, which ismovable in the booth 2, is brought into covering relationship to thecathode-ray tube 3 when the cathode-ray tube 3 is placed on the supportbase 5.

The booth 2 is combined with a conveyor for conveying the cathode-raytube 3 into the booth 2. FIGS. 4 and 5 show different layouts for thebooth 2 and the conveyor.

More specifically, in FIG. 4, the conveyor, denoted at 20, is disposedon one side of the booth 2. In operation, the cathode-ray tube 3 isconveyed by the conveyor 20 therealong. When the cathode-ray tube 3reaches the booth 2, it is introduced into the booth 2 through aloading/unloading opening 21 defined in one of the side walls of thebooth 2. After the screen panel 4 of the cathode-ray tube 3 has beencoated, the cathode-ray tube 3 is moved out of the booth 2 through theloading/unloading opening 21 onto the conveyor 20, and then conveyed toa next processing station by the conveyor 20. Thus, the cathode-ray tube3 is conveyed by the conveyor 20 and moved into and out of the booth 2along the directions indicated by the arrows A.

In FIG. 5, the conveyor 20 extends through the booth 2. In operation,the cathode-ray tube 3 is conveyed by the conveyor 20 therealong. Whenthe cathode-ray tube 3 reaches the booth 2, it is introduced into thebooth 2 through a loading opening 22 defined in one of the side walls ofthe booth 2. After the screen panel 4 of the cathode-ray tube 3 has beencoated, the cathode-ray tube 3 is moved out of the booth 2 through anunloading opening 23, which is defined in an opposite side wall of thebooth 2, onto the conveyor 20, and then conveyed to a next processingstation by the conveyor 20. Thus, the cathode-ray tube 3 is conveyed bythe conveyor 20 and moved into and out of the booth 2 along thedirections indicated by the arrows B.

In the layouts shown in FIGS. 4 and 5, the loading/unloading opening 21,the loading opening 22, and the unloading opening 23 are fitted withrespective selectively openable doors 24 such as shutters. After thecathode-ray tube 3 has been introduced into the booth 2, the doors 24are closed to isolate the interior of the booth 2 from the exteriorspace. After the screen panel 4 of the cathode-ray tube 3 has beencoated, the doors 24 are opened to allow the cathode-ray tube 3 to beunloaded from the booth 2 back to the conveyor 20.

As shown in FIGS. 6A and 6B, the cathode-ray tube 3 is supported on apallet 25 while being conveyed by the conveyor 20. In FIG. 6A, thecathode-ray tube 3 is supported on the pallet 25 with its screen panel 4lying vertically. In FIG. 6B, the cathode-ray tube 3 is supported on thepallet 25 with its screen panel 4 lying horizontally.

Operation of the coating device 1 shown in FIG. 1 will be describedbelow.

The clean air 19 whose temperature and humidity have been controlled bythe air-conditioning unit 17 is supplied through the air outlet 16 intothe booth 2, thereby controlling the temperature and humidity in thebooth 2 to be suitable values, respectively. Then, the coating solution6 for producing an anti-dazzling layer, an anti-static layer, or thelike is sprayed from the spray nozzle 7 onto the screen panel 4 of thecathode-ray tube 3. At the same time, the spray nozzle 7 is movedvertically and horizontally by the coating robot 8 to scan the screenpanel 4 along a zigzag pattern, for example.

While the coating solution 6 is being sprayed onto the screen panel 4,dust particles floating in the booth 2 are attracted to thewater-containing member 9 on the inner wall surfaces of the booth 2.Therefore, dust particles in the booth 2 are prevented from beingentrained by the coating solution 6, and hence from being applied to thescreen panel 4. As the air outlet 16 is located relatively near thescreen panel 4, the screen panel 4 is kept clean by the clean air 19that is supplied downwardly from the air outlet 16 and applied directlyto the screen panel 4. Therefore, the clean air 19 is also effective forpreventing dust particles from being attached to the screen panel 4 whenit is coated with the coating solution 6. The coating layer formed onthe screen panel 4 is thus made less defective and higher in quality.

The coating solution 6 applied to the screen panel 4 can be dried atdifferent rates and hence the resulting coating layer on the screenpanel 4 can have different degree of surface roughness depending on thetemperature of the screen panel 4 and the temperature and humidity inthe booth 2. When the coating solution is dried at a higher rate, thesurface roughness of the dried coating layer is larger, and the coatinglayer is more anti-dazzling. When the coating solution is dried at alower rate, since it tends to sag and spread, the surface roughness ofthe dried coating layer is smaller, and the coating layer is moreglossy. To manufacture non-glare cathode-ray tubes, it is necessary toform a highly anti-dazzling layer on the screen panels of thecathode-ray tubes. On the other hand, to manufacture cathode-ray tubeswhich can display sharp images in bright environments, it is necessaryto form a glossy layer on the screen panels of the cathode-ray tubesthough the glossy layer may be less anti-dazzling. The temperature andhumidity in the booth 2 are important as coating conditions to producesuch different coating layers on the screen panels of cathode-ray tubes.

The temperature and humidity in the booth 2 can be controlled by theair-conditioning unit 17 which controls the temperature and humidity ofthe clean air 19 to be introduced through the air outlet 16 into thebooth 2 and also by the air discharge port 27. Therefore, the rate atwhich the coating solution 6 on the screen panel 4 is dried can becontrolled to form a desired coating layer on the screen panel 4. Theair-conditioning unit 17 controls the humidity in the booth 2 in view ofthe humidifying effect of the water-containing member 9 as the watercontained in the water-containing member 9 tends to vaporize into thebooth 2.

FIG. 7 shows a cathode-ray tube 3 having a screen panel 4 coated with adouble-layer anti-dazzling layer 31 which is composed of a visible-lightabsorbing layer 31a containing a black dye and an anti-static layer 31bcontaining an inorganic metal compound.

Now, a process of manufacturing the double-layer anti-dazzling layer 31shown in FIG. 7 will be described below.

The cathode-ray tube 3 that has been manufactured according to thenormal fabrication process is placed in the booth 2 while the screenpanel 4 is being maintained at a predetermined temperature. An ethylsilicate solution containing 0.1 to 0.5 wt % of a black dye mainlycomposed of carbon powder and 1 to 10 wt % of light-dispersing SiO₂powder is sprayed onto the screen panel 4 at a rate ranging from 0.2 to0.5 ml/sec., thus forming the visible-light absorbing layer 31a.

Then, an ethyl silicate solution containing 40 to 60% of powder of anelectrically conductive metal oxide such as of tin oxide, indium oxide,or the like and 1 to 10 wt % of light-dispersing SiO₂ powder is sprayedonto the visible-light absorbing layer 31a on the screen panel 4 at arate ranging from 0.2 to 0.5 ml/sec., thus forming the anti-static layer31b.

Thereafter, the layers 31a, 31b are baked at a temperature ranging from150° to 200° C. for a time period ranging from 10 to 30 minutes,vaporizing the ethyl component. The double-layer anti-dazzling layer 31is now completed.

When the ethyl silicate solutions are applied to form the visible-lightabsorbing layer 31a and the anti-static layer 31b, double-layeranti-dazzling layers 31 of different properties may be produced bycontrolling the temperature of the screen panel 4 and the temperatureand humidity in the booth 2.

Specifically, if the screen panel 4 is of a temperature of or lower than100° C., e.g., of about 45° C., and the temperature and humidity in thebooth 2 are 25°±5° C. and 50 to 60%, respectively, then the coatedanti-dazzling layer 31 is high in its anti-dazzling effect.

If the screen panel 4 is of a temperature of 30°±10° C., e.g., of about30° C., and the temperature and humidity in the booth 2 are 25°±5° C.and 70±10%, respectively, then the coated anti-dazzling layer 31 is lowin its anti-dazzling effect and highly glossy, e.g., has a gloss valueof 80 or more.

As shown in FIGS. 4 and 5, after the cathode-ray tube 3 has beenintroduced into the booth 2, the door 24 in the loading/unloadingopening 21 or the doors in the loading and unloading openings 22, 23 areclosed to isolate the interior of the booth 2 from the exterior space,as described above. Since the booth 2 is substantially fully closed, thetemperature and humidity in the booth 2 can be easily controlled, andthe coating solution 6 can be applied neatly to the screen panel 4 whilethe clean air 19 is being supplied constantly without disturbance.Consequently, the coated layer on the screen panel is high in quality.The cathode-ray tube with the high-quality coated layer is highlyreliable in operation.

The coating device 1 according to the present invention may be used toform a single anti-static layer or a single anti-dazzling layer, ratherthan the double-layer anti-dazzling layer 31, on the screen panel 4.

Having described preferred embodiments of the invention with referenceto the accompanying drawings, it is to be understood that the inventionis not limited to that precise embodiments and that various changes andmodifications could be effected by one skilled in the art withoutdeparting from the spirit or scope of the invention as defined in theappended claims.

What is claimed is:
 1. A coating device for coating a cathode-ray tubewith a layer, comprising:a booth having means for supporting acathode-ray tube to be coated, said booth having sidewalls and an upperwall; spraying means in said booth for spraying a coating solution ontothe cathode-ray tube so as to form a layer on the cathode-ray tube;water-containing means for absorbing dust particles floating in saidbooth being mounted on inner wall surfaces of said booth; and watersupply means for supplying water to said water-containing means beingconnected to said booth.
 2. A coating device according to claim 1,wherein said water-containing means comprises sponge walls attachedrespectively to said inner wall surfaces of said booth, and water feedpipes disposed in said sponge walls and connected to said water supplymeans.
 3. A coating device according to claim 2, wherein said upper wallis a slanted upper wall and one of said sponge walls being attachedcomplementarily to said slanted upper wall.
 4. A coating deviceaccording to claim 1, further comprising air-conditioning means beingconnected to the booth for controlling the temperature and humidity inthe booth, said air-conditioning means having a filter and havingexhaust means connected to a discharge port of the booth for exhaustingthe interior of the booth.
 5. A coating device according to claim 4,wherein the air-conditioning means includes an air outlet opening intothe booth to supply air directly toward the cathode-ray tube.
 6. Acoating device according to claim 4, wherein the exhaust means includesa hood disposed in said booth adjacent the discharge port for coveringthe cathode-ray tube.
 7. A device according to claim 1, wherein at leastone wall of the booth has an opening with a door and the device hasconveyor means for conveying and introducing the cathode-ray tubesthrough the opening to the means for supporting.
 8. A coating deviceaccording to claim 7, wherein said conveyor means is disposed on oneside of said booth.
 9. A coating device according to claim 7, whereinsaid booth has two walls with openings and said conveyor means extendsthrough said two openings of the booth.